Head structure for spark plugs



W. S. THOMAS.

HEAD STRUCTURE FOR SPARK PLUGS. APPLICATION FILED Nov.1a, 1920.

1,41 1,229, Patented Mams, 1922.

To all 'whom it 'may concern:

WILLIAM s. rHoMAs-or ARosEnnE PARK, NEW JERSEY.

HEAD STRUCTURE RoR sPARx PLUGS.

- Specification of Letters Patent. Patented D131. 2S, 1922.

` Application filed November 16, '1920. lSeral 110,424,436.

Be it knownthaty I, WTLLIAM S.l THOMAS,

, a citizen of the United States, vresiding at Roselle Park, inthe county of Elizabeth and rState of New Jersey, have invented certain new and useful Improvements in Head Structures for Spark Plugs, of which the following is a specification. y

`@ne object of my invention is to provide an Iimproved head structure for spark plugs which willl be of particularadvantage when used vin internal combustion engines and will vserve to protect the insulator'thereof froin'contamination with oils and moist-ure. Another'object is to so make my improved head structure that it will effectively form a seal to prevent the leakage of the products of combustion upwardly from the cavity in the insulator casing.

A still `further Objectis to so design the parts lof my invention that they can be quickly put togetherl so "that the resulting structure canV be .cheaply manufactured. These objects, and otherY advantageous ends which will be described hereinafter, T attain in theV followingmanner, reference being'had tothe accompanying drawings in which?- ,y Figure lis anelevation illustrating my ,inventionV in connection with an insulated electrodefor spark plugs; part ofthe same beingshown in section to'more clearlyillustratefthe `featuresfof the invention, Figure 2 `is an elevation of certain of the parts' of my invention and drawnv on a larger scale than that shown in Figure 1,

Figure 3 is an inverted vplan, View ofthe structure shown in Figure 2, and

Figure 4 is an enlarged fragmentary section of certain of the parts shown in Figure 1 and illustrated on a greatly increased scale.

Referring to the drawings, 5 represents an electrode insulator casing whichv may be made of porcelain. This casing has a cavity 6 which leads downwardly from its top surface 7. A metallic head 8 includes plug portion 9 which extends downwardly into the cavity 6 and a. fiange portion 10 adapted to abut the top surface 7 of the porcelain insulator casing 5. Both the plug portion 9 and the flange portion 10 of the head 8 vare externally knurled; the plug portion 9 having its knurled ribs extending at a slant downwardly as clearly lshown at 11. in Figure 2 while the under surface of the flange portion ll() has curved ribs l2 as clearly shown in Figure 3. The peripheral surface of the flange portion is also knurled to provide ribs 13 which slant as shown in Figure 9. A screw threaded stem lll is preferably formed integral with the head 8 andisadapted toreceive a binding nut 15 and a cap nut 16 as shown in Figure l.

The plug portion 9 of the head 8 has an electrode rod 17 secured thereto so that the head 8 in the operation of the plug will serve as a conductor of electric current to the electroderod k17 by the attachment of the usual electric conduit wire to the head 8 through the medium of the capl nut 16.

ln applying the head 8 and electrode rod 17 tothe insulator casing 5 the outer surface of the plug portion9 and the under surface. of the iange portion 10` is coated with cement 18and the plug is forced downwardly `within the cavity 6; the electrode rod extending down through the cavity 6 with its lowerend portion projecting beyond the bottom of the casing 5 for sparking purposes. Vhen'the head is forced downwardly vsaid cement 18 penetrates between the ribs or knurled parts of the plug and lflange portions and also engages the porcelain `insulator casing 5 at the top sur` face 7 andv the inner surface forming the cavity 6. i f After Vthe above mentionedoperation, `the structure is baked to harden and set the cementa'nd cause it to Vadhere tothe porcelain 'insulator and to the head. After this operation acap y19 having a skirt flange 20v is placed over the flange portion 10 of the head 8; Vsaid skirt flange 2O ofthe cap 19 being of sufficient depth as to extend below the *topsurface 7 of the insulator casing 5. A layer or coating 21 of cement is interposed between the inner surface of the cap 19 and the outer surfaces of the flange portion 10 and porcelain insulator casing y5 so that `a portion of the cement 20 extends annularly around the peripheral surfare of the flange portion 10 of the head 8 and across the cement coating 18 between the flange portion 10 and the casing 5.y Thus a double seal is provided by the cement coatings 18 and 2l as clearlyf shown in Figure 4E so that during the use of a plug made in accordance with Vmy present invention if -there would be any possibility of leakage of gases upwardly through the cavity 6 which would work either way, laterally between the cement 18 and either the head or the insulator casing, the part 22 of the cement 21 would serve as a second seal and prevent the escape of the gas to the atmosphere.

It has been found by tests that this gas leakage under ordinary conditions is intermittent and I have found that by providing the second seal namely the cement 2l which is confined within the cap 19 that the escape of such gas under pressure can be posis tively prevented. If this leakage is prevented the value of theinsulator will consequently be greatly improved since there will be less possibiity of impairing the electrede rod which occurs if subjected to the gases during passage of the gases through the insulator casing cavity. Furthermore by providing a head constructed in accord ance with that above described there is practically no chance for the head to work loose from vthe insulator casing since the arrange ment of the knurled surfaces including the ribs serve as efficient means for binding the head to the insulator and no amount of necessary manipulation of the cap nut 16 or binding nut l5 will serve to loosen the head from the insulator casing.

While I have described my invention as taking a particular form, it will be understood that the various parts of my invention may be changed without departing from the spirit thereof, and hence I do not limit myself to the precise construction set forth, but consider that I am at liberty to make such changes and alterations as fairl come within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is l. The combination in a spark plug of an insulator casing; an electrode head having a flange portion opposed to the end of Said casing and cemented thereto; a cap for covering said flange portion and said end 0f the casing; and cement within said cap and extending across the parting between the flange portion and said end of the casing; substantially as described.

2. The combination in a spark plug of an electrode insulator casing having a cavity cxtending downwardly from one end; an electrode head having a flange for abutment with the end of said casing; a plug portion for fitting within said cavity; cement interposed between said easing, plu and flange portions; a cap fitting over said flange portions; and cement interposed between said cap and flange portion, said latter cement having' a part bridging the arting between the flange and said end o the casing; substantially as described.

The combination in a spark plug of an electrode insulator casing having a cavity extending' downwardly from one end; an electrode head having a flange for abutment with the end of said casing; a plug portion for fitting within said cavity; cement interposed between said casing, plug and flange portions; a cap fitting over said flange portions; and cement interposed between said cap and flange portion, said latter Cement having a part bridging the parting between the flange and said end of the casing, said head having knurled portions in enga ement with said first cement; substantially as described.

4t. The combination in a spark plug of an electrode insulator casing having a cavity extending downwardly from one end; an electrode head having a flange for abutment with the end of said casing; a plug portion for fitting within said cavity; cement interposed between Said casing, plu and flange portions; a cap fitting over sai flange portions; and cement interposed between said cap and flange portion, said latter cement having a part bridging the parting between the flange and said end of the casing, said flange having knurled portions on its under surface for engagement with said first cement; substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

IVILLIAM S. THOMAS. lVitnesses:

ELIZABETH Gamin, Unas. E. PoTTs. 

